The present invention relates in general to medical and surgical instruments, and more particularly to fluid injection or discharge devices.
The present invention has particular utility when used in connection with treating arteriosclerosis problems where an expandable balloon catheter is inserted into an artery and filled with a fluid to expand and collapse obstructing cholesterol deposits on the walls of arteries. It is a conventional practice to inject fluid into the balloon catheter through a connecting tube by a hypodermic syringe, or similar instrument. Other fluid injection devices are disclosed in U.S. Pat. Nos. 2,892,457 and 3,474,787.
the pressure that the balloon exerts on the artery walls is critical in compacting the desired amount of cholesterol deposits against the artery walls, and is directly proportional to the amount of fluid injected into the balloon catheter. The balloon pressure is also critical as excessive pressure may rupture the balloon or injure the delicate artery walls. The traditional practice of injecting fluid into such a type of caatheter with a conventional syringe instrument, as noted above, has met with varying degrees of success, when properly used.
One shortcoming of the use of the noted instruments is that the pressure buildup within the balloon catheter cannot be accurately gauged, except by noting the amount of fluid which has been discharged from the syringe. Because of various balloon catheter elasticities, the amount of fluid discharged from the syringe is not always proportional to the pressure which the balloon exerts on the artery walls. Although a fluroscope is of some help in visually locating the catheter at the proper position within the artery, it cannot accurately gauge the pressure exerted by the balloon catheter on the artery walls. The inadvertent injection of an excessive amount of fluid into the bulb can cause the balloon catheter to rupture.
Another shortcoming of hypodermic syringes in general, as well as the noted instruments in inflating balloon catheters is that such devices are not constructed to attain high balloon pressures, for example one hundred and fifty pounds per square inch.
There is therefore a need for a fluid injection device which indicates pertinent fluid pressures and thereby prevents an excessive amount of presure from developing, whereby the possibility of damaging artery walls or the expandable bulbs themselves is substantially reduced. It is thus the aim of the present invention to provide a medical fluid injection device with a pressure monitor which is ideally suited, but not restricted to the controlled injection of fluid into a balloon catheter.
There is also a need for an instrument which can be initially finger operated, much like a syringe, to quickly discharge fluids under low pressures, and subsequently hand operated to incrementally achieve greater fluid pressures.
Beacuse of advances in the treatment of arteriosclerosis, there is a demand for a high pressure injection gun which is operable with one hand.